Acoustic source localization is a well-studied problem. A special case of such a problem is shooter detection and localization. There are many countersniper systems available. However, their performance in urban environments is usually unsatisfactory. For the countersniper systems that measure phenomena associated with the ejection of a bullet from a gun, such as a muzzle blast or a muzzle flash, they require a direct line of a site to the gun shooter. This significantly limits the coverage efficiency in a dense urban terrain. For the countersniper systems that detect the projectile and try to reconstruct the trajectory, they are typically accurate in their bearing detection, but not as much as in their range estimation. Furthermore, the environmental conditions associated with active warfare, or even typical peacetime urban noise, aggravate the problem.
The majority of sniper detection systems are acoustic related and most of them measure both a muzzle blast and a shock wave [77]. The ballistic shock wave is a sonic boom generated by a supersonic projectile, and has a specific wave shape based on a diameter and a length of the projectile itself, a distance from the flight path along with the velocity of the projectile [6]. A shock wave form generated by the flight of a projectile is called an N-wave, due to its characteristic shape.
A bullet ears system of BBN Technologies, Cambridge, Mass., measures the time of arrival of a shock wave along with its basic characteristics which enables the estimation of the caliber, the speed and trajectory of the projectile using two small arrays of inexpensive microphones [1]. The bullet ears system also detects a muzzle blast to estimate the range of a shooter. Utilizing two microphone arrays it estimates the origin of the shot within ±2° in bearing and ±10% in range depending on the distance between the two arrays versus the firing range.
All of the conventional systems, either acoustic or others, share one common characteristic. They do not perform well in urban environments. These systems are all centralized in the sense that they rely on a small number of sensors or small sensor arrays, typically one or two. If some of the limited number of sensors do not have direct line of sight, they will not detect the shot. In case of the acoustic systems, the problem becomes much harder due to multi-path effects. Instead of missing a shot, they may pick up echoes resulting in an erroneous location estimate.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.